[llvm] [InstCombine] Simplify select if it combinated `and/or/xor` (PR #73362)

[via llvm-commits]

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@@ -4425,6 +4425,48 @@ Value *llvm::simplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
                                   RecursionLimit);
 }
 
+/// Try simplifying the selection command when condition, trueValue, and
+/// falseValue are combinations of special bitwise operators.
+static Value *simplifySelectBitTestSpec(Value *TrueVal, Value *FalseVal,
+                                        Value *X, Value *Y,
+                                        bool TrueWhenUnset) {
+  // (X & Y) == 0 ? X | Y : X ^ Y   --> X ^ Y
+  // (X & Y) == 0 ? X ^ Y : X | Y   --> X | Y
+  // (X & Y) == 1 ? X | Y : X ^ Y   --> X | Y
+  // (X & Y) == 1 ? X ^ Y : X | Y   --> X ^ Y
+  if (match(TrueVal, m_Or(m_Specific(X), m_Specific(Y))) &&
+      match(FalseVal, m_Xor(m_Specific(X), m_Specific(Y)))) {
+    return TrueWhenUnset ? TrueVal : FalseVal;
+  } else if (match(FalseVal, m_Or(m_Specific(X), m_Specific(Y))) &&
+             match(TrueVal, m_Xor(m_Specific(X), m_Specific(Y)))) {
+    return TrueWhenUnset ? TrueVal : FalseVal;
+  }
+  // (X | Y) == 0 ? X & Y : X ^ Y   --> X ^ Y
+  // (X | Y) == 0 ? X ^ Y : X & Y   --> X & Y
+  // (X | Y) == 1 ? X & Y : X ^ Y   --> X & Y
+  // (X | Y) == 1 ? X ^ Y : X & Y   --> X ^ Y
+  if (match(TrueVal, m_And(m_Specific(X), m_Specific(Y))) &&
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goldsteinn wrote:

Think you have an issue. You can end up matching `X & Y == 0 ? X & Y : X ^ Y` -> `X ^ Y` which isn't valid. You need to either pass  the matching compare binop to `simplifySelectBitTestSpec` or just do the cmp match in this function.

https://github.com/llvm/llvm-project/pull/73362